Chilliwack lake is definitely one of the best boating lakes here in the lower mainland in my opinion due to the lack of people and the absolute beauty of the landscape. I've never been to Harrison lake but I've heard that's a great place to go with a larger boat to explore the entire lake and maybe head up to the hot springs. Cultus lake is the incredibly popular lake around here, and isn't as amazing as many people make it seem. It's incredibly busy on the water and a very touristy lake, but there are many attractions such as water slides, an amusement park, and many more shops and such. Chilliwack lake is just about a 45 minute drive past Cultus, but well worth it. Pitt lake is fairly busy and difficult to find parking, but the lake is fairly interesting with an island in the middle that is interesting to explore as well. I've never been to Stave lake but I've heard good things about that place too. Alouette lake is a decent lake as well, as it is very long and deep with many little places to explore/camp along the shore of you can find a spot. If you have a larger boat and enjoy fishing, I would definitely head out on the ocean and cruise the gulf islands! Full of beauty and nature, these islands are also home to some great fishing and even better people. Anyways, that's just my take on the lower mainland. However my favourite lake so far has to be Chilliwack lake